An example of a link structure for supporting a trunnion of a toroidal continuously variable transmission is disclosed in Tokkai Hei 1-21261 published by the JapanesePatent Office.
In this toroidal type continuously variable transmission, a pair of power rollers is gripped between an input disk and an output disk arranged facing each other, and a rotation of the input disk is transmitted to the output disk via a power roller. The power roller is connected to a trunnion via an eccentric shaft. When this trunnion moves in its axial direction due to an actuator, the power roller performs a swing motion essentially around the trunnion. The contact position of the roller relative to tile input disk and output disk varies according to this oscillation angle, and the rotation ratio transmitted to the output disk from the input disk is therefore made to vary continuously.
The pair of power rollers is gripped between the input disk and the output disk. The magnitude of the rotation torque which can be transmitted is determined by the force with which the rollers are gripped. When this grip force is low, the power roller slips when a large torque acts, and the transmission efficiency of the disk rotation torque drops. It is most desirable that the rotation torque be transmitted equally by both power rollers, and for this purpose the grip pressures on both power rollers must be equalized. When the grip pressure acting on one power roller is low, the transmission torque is limited.
However, insofar as concerns the trunnion, each end of which is connected with a first and second links, a moment according to the direction of rotation acts on the pair of power rollers during power transmission, and the grip pressure on each power roller therefore can become different. Specifically, since the power rollers are arranged facing each other on either side of the rotation axis of the input and output disk, one power roller is pushed into between the input and output disk due to the moment accompanying the rotation, so that the grip force is high, but the other power roller is pushed out of the disks so that the grip force acting on it is low. The torque transmitted by each of the power rollers will therefore be different. Also even if the power rollers are fitted so as to cancel the influence of the aforesaid moment when the toroidal type continuously variable transmission is assembled, if there are still dimensional errors in the power roller fitting position, it will be impossible to set the grip pressure on both power rollers exactly according to design specifications. However, it is very difficult and very costly to completely eliminate dimensional errors.